1. Field of the Invention
The invention relates in general to switch mechanisms, and more particularly to snap switches in which a compression spring or the equivalent thereof moves over dead center, to bias a movable contact element in a generally linear path between make and break positions. In a more particular sense, the invention relates to switches wherein the movable contact element has a slow, double break, and a fast bounce free make.
2. Description of the Prior Art
A wide variety of AC switches has been provided for the market, for use as wall switches in residential and commercial buildings, appliance control switches, and so-called boxless switches used in manufactured homes, to state a few examples of locations and circuits in which switches of this type are commonly installed.
A switch of this type, desirably, should be capable of manufacture at extremely low cost, and should additionally possess many properties known to be highly desirable, and indeed in many cases necessary. Desirably, the switch should incorporate make and break actions which are known to be especially significant in AC circuits. The failure to incorporate these characteristics in an AC switch may in some instances require that the contacts be of heavy, highly expensive material. For example, it is a common practice to employ silver alloy contacts in AC switches, because typically, there is only a small contact area. In these circumstances a material possessing high electrical conductivity is needed to minimize melting or welding of the electrical contacts. It is true, also, that in the absence of a silver alloy contact, as for example where a brass contact is used, adverse electrical phenomena manifest themselves. For example, when brass contacts are employed, a brass vapor is produced in the arc almost inevitably resulting during the break portion of the switch cycle. Brass vapor does not cool quickly enough in half of an AC cycle to condense completely as does silver. As a result, "restrikes" occurring across the contact gap after separation of the contacts may occur. As a result, there may be a rapid deterioration of the switching function or other equally disastrous consequences.
It is also of major importance that an AC switch be capable of passing the stringent testing requirements of Underwriters Laboratories, as well as local, state, and national building codes and standards. Typically, these involve testing the switch for endurance and safe and efficient operation under both light and heavy loads, often with substantial inrush contents.
Also, temperature rise due to electrical resistance at the termination points must be controlled. To meet these exceedingly strict requirements, while yet achieving the equally important goal of permitting manufacture at low cost, has presented a dilemma to manufacturers. The problem they face is that compliance with electrical codes and other requirements can be readily achieved by use of highly expensive switch designs; it is equally easy to produce inexpensive switch designs that are incapable of meeting established, stringent safety and operational requirements. Providing a switch which is both inexpensive and will yet be designed for safe and long operation is a problem which, it is felt, has not yet been fully achieved in the prior art.